Structural Controls on the Edwards Aquifer/Trinity Aquifer Interface in the Camp Bullis Quadrangle, Texas

The purpose of this study was to generate a three-dimensional computer model and predictions of localized fault related deformation in the Edwards Aquifer and the Trinity Aquifer in the study area. The study also provided an analysis of the potential for hydraulic communication across the interface between the two aquifers, taking into account fault-related deformation and juxtaposition of the aquifers across key faults. The study was completed in December 2003 by Southwest Research Institute, San Antonio, Texas. The purpose of the project reported here is to characterize the structural architecture of the Edwards and Trinity Aquifers for the area of the Camp Bullis 7 ½ minute quadrangle, and extending north to include Cibolo Creek in the southern part of the Bergheim 7 ½ minute quadrangle. Included in this analysis are tasks to generate a three-dimensional computer model of the Trinity and Edwards Aquifer, and perform field investigations to characterize the mechanisms and products of localized fault-related deformation in the Edwards and Trinity Aquifers in and near the study area. An important objective is to analyze the potential for communication between the Edwards Aquifer and the Trinity Aquifers, taking into account fault-related deformation and juxtaposition of the aquifers across key faults. Results of the project show the aquifer architecture throughout the study area, the location and interpreted geometry of the most important mapped faults in the study area, and the deformation mechanisms and deformation style in fault zones in the rocks of both the Edwards and Trinity Aquifers. The three-dimensional geologic framework model of the Camp Bullis area reveals (i) juxtaposition of permeable and relatively impermeable hydrogeologic units, (ii) structural thinning of the Edwards Aquifer and Trinity Aquifers, (iii) potential for cross-fault communication between the Trinity and Edwards Aquifers, (iv) faults expressed on the surface as potential infiltration pathways, and (v) maximum offset concentrated alo

Structural Controls on the Edwards Aquifer/Trinity Aquifer Interface in the Camp Bullis Quadrangle, Texas

The purpose of this study was to generate a three-dimensional computer model and predictions of localized fault related deformation in the Edwards Aquifer and the Trinity Aquifer in the study area. The study also provided an analysis of the potential for hydraulic communication across the interface between the two aquifers, taking into account fault-related deformation and juxtaposition of the aquifers across key faults. The study was completed in December 2003 by Southwest Research Institute, San Antonio, Texas. The purpose of the project reported here is to characterize the structural architecture of the Edwards and Trinity Aquifers for the area of the Camp Bullis 7 ½ minute quadrangle, and extending north to include Cibolo Creek in the southern part of the Bergheim 7 ½ minute quadrangle. Included in this analysis are tasks to generate a three-dimensional computer model of the Trinity and Edwards Aquifer, and perform field investigations to characterize the mechanisms and products of localized fault-related deformation in the Edwards and Trinity Aquifers in and near the study area. An important objective is to analyze the potential for communication between the Edwards Aquifer and the Trinity Aquifers, taking into account fault-related deformation and juxtaposition of the aquifers across key faults. Results of the project show the aquifer architecture throughout the study area, the location and interpreted geometry of the most important mapped faults in the study area, and the deformation mechanisms and deformation style in fault zones in the rocks of both the Edwards and Trinity Aquifers. The three-dimensional geologic framework model of the Camp Bullis area reveals (i) juxtaposition of permeable and relatively impermeable hydrogeologic units, (ii) structural thinning of the Edwards Aquifer and Trinity Aquifers, (iii) potential for cross-fault communication between the Trinity and Edwards Aquifers, (iv) faults expressed on the surface as potential infiltration pathways, and (v) maximum offset concentrated alo

Surface water–groundwater interactions along the Blanco River of central Texas, USA

The Blanco River is a very important resource for water supplies in the Hill Country of central Texas. Some communities and properties along the river use the surface water directly. But, the Blanco River is more significant in the role it plays in providing recharge to the karstic Trinity and Edwards Aquifers. Recent studies have given a better indication of the complexity of the interactions between surface water and groundwater in the area. Besides being a water supply to a population of several hundred thousand people, water originally flowing in the Blanco River provides flow to springs that host a number of endangered species. The Blanco River is characterized by alternating gaining and losing stretches due to the presence of springs that discharge water into the river and swallets that drain water from the river. Trinity units outcrop in the western part of the study area, and Edwards units outcrop in the eastern part of the study area. Normal faulting along the Balcones Fault Zone has juxtaposed the older, stratigraphically underlying Trinity units against the Edwards units to the east. The region consists primarily of Lower Cretaceous limestone, dolomite, and marl. One of the more significant springs along the Blanco River is Pleasant Valley Spring. During below-average flow conditions, Pleasant Valley Spring becomes the headwaters of the Blanco River even though the headwaters, under wet conditions, are about 50 km upstream. These studies, summarized in this paper, provide a greater understanding of the surface water and groundwater resources in the area which will help guide policies for groundwater management and preservation of springflows and groundwater supplies